【HDU】2136 - Largest prime factor（打表）

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Largest prime factor

Time Limit: 5000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 11144 Accepted Submission(s): 3942

Problem Description

Everybody knows any number can be combined by the prime number. Now, your task is telling me what position of the largest prime factor. The position of prime 2 is 1, prime 3 is 2, and prime 5 is 3, etc. Specially, LPF(1) = 0.

Input

Each line will contain one integer n(0 < n < 1000000).

Output

Output the LPF(n).

Sample Input

   1
2
3
4
5

Sample Output

   0
1
2
1
3

Author

Wiskey

Source

HDU 2007-11 Programming Contest_WarmUp

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代码如下：

#include <cstdio>
#include <stack>
#include <queue>
#include <cmath>
#include <vector>
#include <cstring>
#include <algorithm>
using namespace std;
#define CLR(a,b) memset(a,b,sizeof(a))
#define INF 0x3f3f3f3f
#define LL long long
#define MAX 1000000
int pos[MAX+11];
int ant = 1;
int main()
{
	for (int i = 2 ; i <= MAX ; i++)
	{
		if (!pos[i])
		{
			pos[i] = ant;
			for (int j = i + i ; j <= MAX ; j += i)
				pos[j] = ant;
			ant++;
		}
	}
	int n;
	while (~scanf ("%d",&n))
		printf ("%d\n",pos[n]);
}